Field of the Disclosure
Embodiments of the present invention relate to an organic light emitting display device, and more particularly, to a rollable organic light emitting display system.
Discussion of the Related Art
An organic light emitting display device (OLED) is a self light emitting display device. The organic light emitting display device may be fabricated to be lightweight and have a slim size as it does not need a separate light source unlike a liquid crystal display device (LCD). Also, the organic light emitting display device is favorable in view of power consumption due to low voltage driving and also is excellent for color gamut, a response speed, a viewing angle, and a contrast ratio (CR).
Recently, a flexible display device, which may display an image while being bent by the use of a flexible material such as plastic or metal foil instead of an inflexible material such as a glass substrate, has been manufactured. Furthermore, a rollable display device, which may be rolled, has been manufactured.
FIG. 1A is a plane view illustrating a related art organic light emitting display device.
As shown in FIG. 1A, a display area (DA) is disposed on a substrate 1 of the related art organic light emitting display device, and a non-display area (NA) is disposed in the periphery of the display area (DA). Herein, a gate pad (GP) and a data pad (DP) are provided in the non-display area (NA). For example, the gate pad (GP) is disposed at a left side of the display area (DA), and the data pad (DP) is disposed at a lower side of the display area (DA). FIG. 1B is a cross sectional view illustrating the related art organic light emitting display device, and FIG. 1B is a cross sectional view along I-I of FIG. 1A.
As shown in FIG. 1B, the related art organic light emitting display device may include the substrate 1, a thin film transistor layer 2, an organic light emitting diode layer 3, an encapsulation layer 5 and an encapsulation substrate 7.
In the display area (DA) of the substrate 1, there are the thin film transistor layer 2, the organic light emitting diode layer 3, the encapsulation layer 5 and the encapsulation substrate 7 which are sequentially stacked thereon.
The thin film transistor layer 2 is formed on the substrate 1. Although not shown, the thin film transistor layer 2 may include a switching thin film transistor and a driving thin film transistor which are provided by each pixel.
The thin film transistor layer 2, the encapsulation layer 5 and the encapsulation substrate 7 extend to the non-display area (NA) of the substrate 1. The thin film transistor layer 2 includes the gate pad (GP) formed in the non-display area (NA) of the substrate 1, wherein the gate pad (GP) is connected with an external circuit driver such as a flexible printed circuit film. The gate pad (GP) is prepared in the non-display area (NA) of the substrate 1, whereby a length of the substrate 1 is greater than a length of the encapsulation substrate 7.
The organic light emitting diode layer 3 is formed on the thin film transistor layer 2. Although not shown, the organic light emitting diode layer 3 may include a cathode, an anode and an emitting layer provided between the cathode and the anode.
The encapsulation layer 5 is formed on the organic light emitting diode layer 3. The encapsulation layer 5 is disposed to cover the organic light emitting diode layer 3, and is provided to reduce a permeation of moisture into the inside of the organic light emitting diode layer 3.
The encapsulation substrate 7 is formed on the encapsulation layer 5. The encapsulation substrate 7 together with the encapsulation layer 5 protects the organic light emitting diode layer 3 from moisture and oxygen provided from the external.
The related art organic light emitting display device has the following disadvantages.
Structurally, the related art organic light emitting display device is weak to an external impact. Thus, the related art organic light emitting display device may be easily damaged by an external impact. In more detail, if an external impact is applied from a direction of a lower surface of the substrate 1 or a direction of an upper surface of the encapsulation substrate 7, the substrate 1 and the encapsulation substrate 7 may absorb the external impact somewhat, whereby there may be no significant problems. However, an additional impact-absorbing element is not provided at a lateral side of the substrate 1. Thus, if the external force is applied from a lateral direction of the substrate 1, the lateral side of the substrate 1 may be easily damaged. Especially, the length of the substrate 1 is greater than the length of the encapsulation substrate 7, that is, the substrate 1 protrudes more than the encapsulation substrate 7. In comparison to the encapsulation substrate 7, if the external impact is applied to the substrate 1, there is a high possibility of a damage on the lateral side of the substrate 1. Also, the substrate 1 is formed of glass which endures a high-temperature deposition process for formation of the thin film transistor layer 2. Meanwhile, in case of the encapsulation substrate 7, there is less need for enduring a high temperature because the encapsulation substrate 7 is formed on the organic light emitting diode layer 3 after forming the thin film transistor layer 2 and the organic light emitting diode layer 3 on the substrate 1. Thus, the encapsulation substrate 7 may be formed of a plastic material or a metal material in a bottom emission method. If the external impact is applied, the substrate 1 of the glass material may be damaged in comparison to the encapsulation substrate 7 of the plastic or metal material.
Also, in case of the rollable organic light emitting display device, it is difficult to prepare an additional protection case since a roll-in operation and a roll-out operation are repetitively carried out. Accordingly, in case of the rollable organic light emitting display device, the lateral side of the substrate 1 is exposed to the external without any protection element, whereby the substrate 1 may be damaged by the externally-applied physical impact.